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[107.190.31.17]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc154f1e54asm870811a12.0.2026.08.19.10.25.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2026 10:25:34 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 19 Aug 2026 13:25:33 -0400 Message-Id: Cc: , "Alexei Starovoitov" , "Daniel Borkmann" , "Andrii Nakryiko" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" , "Martin KaFai Lau" , "Song Liu" , "Yonghong Song" , "Jiri Olsa" , "Emil Tsalapatis" , "Ihor Solodrai" , "Yuan Chen" Subject: Re: [PATCH bpf-next v3 2/3] bpf, arena: fix range_tree_set inconsistency on kmalloc_nolock failure From: "Emil Tsalapatis" To: , X-Mailer: aerc 0.21.0-0-g5549850facc2 References: <20260810134800.2875487-1-chenyuan_fl@163.com> <20260810134800.2875487-3-chenyuan_fl@163.com> In-Reply-To: <20260810134800.2875487-3-chenyuan_fl@163.com> On Mon Aug 10, 2026 at 9:47 AM EDT, chenyuan_fl wrote: > From: Yuan Chen > > range_tree_set() pre-allocates the node needed for a brand-new range > before calling range_tree_clear(), so an allocation failure returns > -ENOMEM without having modified the tree (previously the overlapping > nodes were already removed by range_tree_clear() before the allocation > was attempted, permanently losing the cleared sub-ranges). > > Signed-off-by: Yuan Chen Reviewed-by: Emil Tsalapatis > --- > kernel/bpf/range_tree.c | 45 +++++++++++++++++++++++++++++++---------- > 1 file changed, 34 insertions(+), 11 deletions(-) > > diff --git a/kernel/bpf/range_tree.c b/kernel/bpf/range_tree.c > index 15b588377a76..54055b1fe541 100644 > --- a/kernel/bpf/range_tree.c > +++ b/kernel/bpf/range_tree.c > @@ -199,6 +199,7 @@ int is_range_tree_set(struct range_tree *rt, u32 star= t, u32 len) > int range_tree_set(struct range_tree *rt, u32 start, u32 len) > { > u32 last =3D start + len - 1; > + struct range_node *new_rn =3D NULL; > struct range_node *right; > struct range_node *left; > int err; > @@ -208,20 +209,40 @@ int range_tree_set(struct range_tree *rt, u32 start= , u32 len) > if (left && left->rn_start <=3D start && left->rn_last >=3D last) > return 0; > =20 > + /* > + * A new node is needed only when the range has no adjacent free > + * range on either side. This is known before clearing: any range > + * covering start - 1 or last + 1 survives the clear as an adjacent > + * piece. Allocate only in that case, before modifying the tree, so > + * a failure leaves the range tree unmodified > + */ > + left =3D range_it_iter_first(rt, start - 1, start - 1); > + right =3D range_it_iter_first(rt, last + 1, last + 1); > + if (!left && !right) { > + new_rn =3D kmalloc_nolock(sizeof(struct range_node), > + __GFP_ACCOUNT, NUMA_NO_NODE); > + if (!new_rn) > + return -ENOMEM; > + } > + > /* Clear out everything in the range we want to set. */ > err =3D range_tree_clear(rt, start, len); > if (err) > - return err; > + goto out_free_new; > =20 > /* Do we have a left-adjacent range ? */ > left =3D range_it_iter_first(rt, start - 1, start - 1); > - if (left && left->rn_last + 1 !=3D start) > - return -EFAULT; > + if (left && left->rn_last + 1 !=3D start) { > + err =3D -EFAULT; > + goto out_free_new; > + } > =20 > /* Do we have a right-adjacent range ? */ > right =3D range_it_iter_first(rt, last + 1, last + 1); > - if (right && right->rn_start !=3D last + 1) > - return -EFAULT; > + if (right && right->rn_start !=3D last + 1) { > + err =3D -EFAULT; > + goto out_free_new; > + } > =20 > if (left && right) { > /* Combine left and right adjacent ranges */ > @@ -241,14 +262,16 @@ int range_tree_set(struct range_tree *rt, u32 start= , u32 len) > right->rn_start =3D start; > range_it_insert(right, rt); > } else { > - left =3D kmalloc_nolock(sizeof(struct range_node), __GFP_ACCOUNT, NUMA= _NO_NODE); > - if (!left) > - return -ENOMEM; > - left->rn_start =3D start; > - left->rn_last =3D last; > - range_it_insert(left, rt); > + /* No adjacent ranges; use the pre-allocated node */ > + new_rn->rn_start =3D start; > + new_rn->rn_last =3D last; > + range_it_insert(new_rn, rt); > } > return 0; > + > +out_free_new: > + kfree_nolock(new_rn); > + return err; > } > =20 > void range_tree_destroy(struct range_tree *rt)